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The Hypatia 308 High Current Sourcing Milliohm Meter provides efficient and accurate stress based testing of safety ground systems to insure that they meet certain performance standards of safety certification agencies such as UL, ETL, TUV, CSA, VDE, BABT and others. It utilizes probes with built in remote sensing or, for multi-point testing or the highest precision measurements, auxiliary Kelvin sense probes. In addition to ground impedance measurements, it can provide and accurately monitor the high currents necessary to test ground system endurance as is required for ground guards on etched circuit boards or in power transformers or other components.
Functionally, the Hypatia 308 Milliohm Meter provides low voltage AC current adjustable to 60 amps rms at the frequency of the power source (typically 60 Hz). This current and the voltage differential at the probe tips it induces are both measured by means of digital signal processing in true rms and divided to yield impedance. The value of the current is displayed continuously on a bar graph, and may be selected to be displayed on the primary digital readout at the same time. Normally, however, the digital readout is selected to display the impedance of the device under test. While the impedance measurement range is 0 to 100 ohms, the center of interest is usually in the 0 to 100 milliohm area. Basic specified accuracy is ± 1% for both impedance and current.
Specifications
| Impedance Measurement: |
| Accuracy | ± 1% of reading (when the test current is > 500µ / impedance in Ohms and > 30 mA) |
| Range | 0 to 100 Ohms |
| Digital Current Measurement | Accuracy | ± 1% of reading ± 4 mA |
| Range | 0 to 144 Amps rms |
| Bar Graph Current Measurement | Accuracy: | ± 1% of reading ± 4 mA at transition points (every 2.5 Arms) |
| Range | 2.5 to 77.5 Amps rms (0 to 2.5 Arms implied) |
| Digital Timer | Accuracy | ± .1% (Digital Timer and Audio / Visual Alerts applicable to Model 309 or, if server driven, Model 308) |
| Range | 1 second to 59 minutes, 59 seconds (extended times possible under server software) |
| Audio / Visual Alerts | When enabled, sounds and flashes when any user specified test current or impedance limit is violated. |
| Accuracy: Logically detected. The accuracy therefore exactly matches the accuracy of associated measurements. |
| Operating Duty Cycle | Continuous to test currents of 35 Amps |
| Derate linearly to 50% duty cycle at 60 Amps |
| Maximum Cycle Period: 35 to 60 Amps: 4 Minutes |
| Maximum allowed common mode voltage to ground: 50 Vrms, 71 Vpeak or dc |
| Maximum normal mode open circuit probe source voltage (at 132 Vrms line voltage) | 8.6 Vrms, 12.1 Vpeak |
| Input Power Requirements | 90 to 132 Volts rms |
| 48 to 66 Hertz sine wave |
| Maximum Power: 396 Watts (3.0 Arms at 132 Vrms) |
| Check Resistor | Resistance: 100 milliohms ± 1% |
| Maximum continuous current: 17.5 Amps |